1. Field of the Invention
The invention relates to a liquid crystal projector apparatus and more particularly to a liquid crystal projector apparatus adapted to prevent deterioration in contrast and uniformity due to properties of dependence on viewing angles.
2. Description of the Related Art
A projector apparatus for projecting an image on a screen under magnification and thus implementing a large screen is in widespread use as an image display apparatus for indoor and outdoor use. The projector apparatus is broadly divided into a projector apparatus (a CRT projector apparatus) for projecting exiting light from a fluorescent screen of a CRT onto a screen and a projector apparatus for projecting modulated light onto a screen after modulating light emitted from a light source by means of a spatial light modulator, and, in the case of the latter, a projector apparatus (a liquid crystal projector apparatus) using a liquid crystal panel as the spatial light modulator is in the mainstream.
FIG. 1 shows an example of a configuration of an optical system of a liquid crystal projector apparatus of the related art (an optical system of a three-panel transmission type liquid crystal projector apparatus using three transmission type liquid crystal panels for RGB).
A light source 11 includes a lamp 12 (e.g., a xenon lamp), and a reflector 13 for reflecting light (white unpolarized light) emitted from the lamp 12 so as to form the light into a bundle of rays having a predetermined angle of divergence. Light emitted from the light source 11 passes through microlens arrays 14 and 15 and a polarizer 16 in sequence.
The microlens arrays 14 and 15 comprise an array of a plurality of microlenses 14a and an array of a plurality of microlenses 15a, respectively (for example, each lens has a diameter of about 1 mm to 5 mm). Each lens 14a is rectangular and similar in shape to a panel surface of each of transmission type liquid crystal modules 28, 29 and 30 in order that light exiting from the lens 14a may be focused on a panel surface of each of liquid crystal panels 42 to be described later.
The microlens array 15 is located substantially on a focal point of the lenses 14a. One each of the lenses 15a corresponds to one each of the lenses 14a and each lens 15a has such a shape that the most possible light exiting from the corresponding lens 14a can enter into the lens 15a. 
The microlens arrays 14 and 15 allow the emitted light from the light source 11 to uniformly enter into the panel surface of the liquid crystal panel, thereby serving to improve uniformity of an image to be displayed on a screen (the uniformity refers to the uniformity of brightness or color for displaying an image of the same brightness or color over the overall screen).
The polarizer 16 is a device for converting most of incoming unpolarized light into linearly polarized light (e.g., p-polarized light) and then allowing the linearly polarized light to exit. The polarizer 16 serves to improve the efficiency of utilization of the emitted light from the light source 11 and also serves to improve contrast of an image to be displayed on a screen by increasing the quantity of exiting light from the liquid crystal panel at the time of white display.
The p-polarized light exiting from the polarizer 16 is focused and impinges on a dichroic mirror 18 by a lens 17. For example, the dichroic mirror 18 transmits red light of RGB light and reflects green light and blue light. Red p-polarized light passing through the dichroic mirror 18 is reflected by a mirror 19, and the reflected light is focused on and enters into a liquid crystal module 28 by a lens 20.
Green p-polarized light and blue p-polarized light reflected by the dichroic mirror 18 impinge on a dichroic mirror 21. For example, the dichroic mirror 21 transmits blue light and reflects green light. The green p-polarized light reflected by the dichroic mirror 21 is focused on and enters into a liquid crystal module 29 by a lens 22.
The blue p-polarized light passing through the dichroic mirror 21 is repeatedly focused and reflected by a lens 23, a mirror 24, a lens 25, a mirror 26 and a lens 27, and then the light enters into a liquid crystal module 30.
The liquid crystal modules 28, 29 and 30 have the same configuration. FIG. 2 shows an example of a configuration of an optical system of each of the liquid crystal modules 28, 29 and 30. A sheet polarizer 41 is located close to the entry side of the transmission type liquid crystal panel 42, and a polarizer 47 is located close to the exit side of the liquid crystal panel 42. The polarizer 41 has the orientation of the axis of polarization (the axis of light transmission) which is determined so as to allow the p-polarized light to pass through the polarizer 41. Therefore, the red p-polarized light, green p-polarized light and blue p-polarized light entering into the liquid crystal modules 28, 29 and 30, respectively, pass through the polarizers 41 as they are, and enter into the liquid crystal panels 42.
The liquid crystal panel 42 is a TN (twisted nematic) liquid crystal panel, and changes the locus of a resultant electric field vector of light passing through liquid crystal molecules according to the level of a voltage applied to the liquid crystal molecules. A voltage is applied to the liquid crystal molecules of pixels of the liquid crystal panels 42 of the liquid crystal modules 28, 29 and 30 in normally white mode according to the levels of video signals for red, green and blue. For example, an active matrix drive system is adopted as a system for driving the liquid crystal panel 42.
Microlenses 44, one each of which corresponds to one each of the pixels, are provided in a substrate 43 on the entry side of the liquid crystal panel 42. The microlenses 44 are lenses for focusing light incident on the corresponding pixels on effective display area portions of the pixels (i.e., portions having no electrode, switching device and so on and thus capable of allowing light to pass through the portions). The microlenses 44 serve to substantially increase an ratio aperture of the liquid crystal panel 42 and also serve to improve the contrast of an image by increasing the quantity of exiting light from the liquid crystal panel 42 at the time of white display.
Light, which passes through a liquid crystal layer 45 of the liquid crystal panel 42 and then exits through a substrate 46 on the exit side, enters into the polarizer 47. The orientation of the axis of polarization of the sheet polarizer 47 is perpendicular to that of the polarizer 41, and therefore the polarizer 47 allows s-polarized light to pass through the polarizer 47.
Red s-polarized light, green s-polarized light and blue s-polarized light passing through the polarizers 47 of the liquid crystal modules 28, 29 and 30 enter into a dichroic prism 31 from three directions, as shown in FIG. 1. The dichroic prism 31 has a filter film 31a for transmitting green light from the liquid crystal module 29 and reflecting red light from the liquid crystal module 28 in the same direction as the green light, and a filter film 31b for transmitting green light from the liquid crystal module 29 and reflecting blue light from the liquid crystal module 30 in the same direction as the green light. The red s-polarized light, green s-polarized light and blue s-polarized light are combined into one bundle of rays by the dichroic prism 31.
The s-polarized light exiting from the dichroic prism 31 is projected onto a screen (not shown) via a projection optical system 32.
As shown in FIGS. 1 and 2, the liquid crystal projector apparatus of the related art is devised to improve the uniformity by the microlens arrays 14 and 15 provided in a lighting optical system for guiding light emitted from the light source 11 to the liquid crystal modules 28, 29 and 30, to improve the contrast by the polarizer 16 provided in the lighting optical system, and to improve the contrast by the microlenses 44 provided in the substrate 43 on the entry side of each of the liquid crystal panels 42 of the liquid crystal modules 28, 29 and 30.
A TN liquid crystal panel and an STN (supertwisted nematic) liquid crystal panel have properties of being incapable of changing the locus of a resultant electric field vector of light incident obliquely on a panel surface according to initial level (according to the level of an applied voltage). This is called properties of dependence on viewing angles.
As shown in FIG. 18, the properties of dependence on viewing angles result from tilt angles (pretilt angles) p1 and p2 of liquid crystal molecules 53 to rubbing directions 51a and 52a of the respective alignment layers of substrates 51 and 52 on the entering and exit sides of a liquid crystal panel, respectively (corresponding to the substrates 43 and 46, respectively, in FIG. 7). Due to the existence of the pretilt angles, when passing through liquid crystal molecules, light incident obliquely on a panel surface produces phase shift between extraordinary light and ordinary light in a plane parallel to the panel surface and also produces phase shift between extraordinary light and ordinary light even in a plane perpendicular to the panel surface. As a result, it becomes impossible to change the locus of a resultant electric field vector of the incident light according to initial level.
In a liquid crystal display using a TN liquid crystal panel or an STN liquid crystal panel, due to the properties of dependence on viewing angles, even in normally white mode, linearly polarized light (e.g., p-polarized light) entering obliquely into the liquid crystal panel through pixels to display black (i.e., pixels to which a voltage is applied so that liquid crystal molecules may be aligned perpendicularly to a substrate) changes into elliptically polarized light, which then exits from the liquid crystal panel through the pixels. Then, s-polarized light component of the elliptically polarized light pass through an analyzer and are then projected onto a screen (that is, black stands out), and therefore the contrast may deteriorate.
FIG. 19 illustrates the correlation between an incident angle of light to a liquid crystal panel and the degree of deterioration in contrast. The greater an incident angle xcex8 becomes, the lower contrast CR becomes, regardless of an incident direction xcfx86 in a plane parallel to a panel surface of the liquid crystal panel.
The degree of phase shifts due to the pretilt angles changes according to a cell gap length of a liquid crystal panel (i.e., a distance between two substrates which liquid crystal molecules are sandwiched between). In the case where the cell gap lengths vary according to parts of the liquid crystal panel, even when an image of the same brightness over the overall screen should be displayed (voltages on the same level are applied to all pixels), the properties of dependence on viewing angles cause variations in the transmittance of light passing through an analyzer after entering obliquely into the liquid crystal panel and then exiting from the liquid crystal panel, according to the parts of the liquid crystal panel, and therefore the brightness of the image may become nonuniform (that is, the uniformity may deteriorate).
As described above, an image display apparatus using a liquid crystal panel may deteriorate in contrast and uniformity due to the properties of dependence on viewing angles resulting from the existence of the pretilt angles. Although a direct-vision type liquid crystal display is designed in consideration of the properties of dependence on viewing angles, a liquid crystal projector apparatus that is a projection type liquid crystal display is not so devised as to improve the contrast and uniformity in consideration of the properties of dependence on viewing angles.
The reason why the direct-vision type liquid crystal display is designed in consideration of the properties of dependence on viewing angles is as follows: the quantity of light entering obliquely into the liquid crystal panel is large because an angle of divergence of light emitted from a light source is great, and moreover a screen is often viewed obliquely, so that the light entering obliquely into the liquid crystal panel and then exiting from the liquid crystal panel reaches to the eyes.
The reason why the liquid crystal projector apparatus is designed without the consideration of the properties of dependence on viewing angles is as follows: the apparatus has been heretofore designed in consideration of only linearly polarized light incident from a direction perpendicular to a panel surface, because a bundle of substantially parallel rays has been emitted from a light source and the emitted rays have entered into the liquid crystal panel via a lighting optical system while remaining substantially parallel.
However, even the liquid crystal projector apparatus recently has had a tendency to increase a range of an incident angle of light to the liquid crystal panel by increasing the angle of divergence of light emitted from the light source or by reducing the f-number of the lighting optical system, for the purpose of displaying a brighter image.
Even in the liquid crystal projector apparatus shown in FIGS. 1 and 2, the f-number of the lighting optical system is reduced so that the incident angle of light to each of the liquid crystal panels 42 of the liquid crystal modules 28, 29 and 30 lies between about plus and minus 10 to 15 degrees, for example. Therefore, p-polarized light entering obliquely into the liquid crystal panel through pixels to display black changes into elliptically polarized light, which then exits from the liquid crystal panel through the pixels, and then s-polarized light components of the elliptically polarized light pass through the polarizer 47 and are then projected onto a screen, so that the contrast deteriorates.
When the cell gap lengths vary according to parts of the liquid crystal panels 42 of the individual liquid crystal modules 28, 29 and 30, or when the cell gap lengths of the liquid crystal panels 42 differ among the liquid crystal modules 28, 29 and 30, the brightness or color of an image to be displayed on a screen becomes nonuniform (that is, the uniformity deteriorates) even when an image of the same brightness or color over the overall screen should be displayed.
Therefore, even the liquid crystal projector apparatus recently has had to prevent deterioration in contrast and uniformity due to the properties of dependence on viewing angles.
Although the liquid crystal projector apparatus is configured so that the incident angle of light to each of the liquid crystal panels lies between about plus and minus 10 to 15 degrees, the liquid crystal projector apparatus has a much narrower range of the incident angle as compared to the direct-vision type liquid crystal display. Therefore, the deterioration in contrast and uniformity cannot be prevented even if a conventional approach for designing the direct-vision type liquid crystal display in consideration of the properties of dependence on viewing angles is adopted for the liquid crystal projector apparatus as it is.
The invention is designed to overcome the foregoing problems. It is an object of the invention to provide a projection type liquid crystal display apparatus, which can improve black-level display and thus can display a higher-contrast image as compared to the related art.
It is another object of the invention to prevent deterioration in contrast and uniformity due to properties of dependence on viewing angles through an approach suitable for a liquid crystal projector apparatus using a TN liquid crystal panel or an STN liquid crystal panel (in particular, a transmission type liquid crystal projector apparatus having liquid crystal panels each having microlenses for increasing a numerical aperture, as illustrated in FIGS. 1 and 2).
A liquid crystal projector apparatus of the invention including: a liquid crystal panel having microlenses for focusing incoming light on effective display area portions of pixels, the liquid crystal panel for changing a locus of a resultant electric field vector of light passing through liquid crystal molecules according to a voltage applied to the liquid crystal molecules; a polarizer for allowing linearly polarized light, which is contained in light emitted from a light source and has one direction of vibration, to enter into the liquid crystal panel; and an analyzer for allowing linearly polarized light, which is contained in light exiting from the liquid crystal panel and has one direction of vibration, to enter into a projection optical system comprises: an optical compensator located between the liquid crystal panel and the analyzer and having birefringence in planes parallel and perpendicular to a panel surface of the liquid crystal panel, the optical compensator for compensating for phase shifts due to pretilt angles by the birefringence when light passes through the liquid crystal molecules after entering obliquely into the liquid crystal panel.
In the liquid crystal projector apparatus, the optical compensator having the birefringence in the planes parallel and perpendicular to the panel surface of the liquid crystal panel is located between the liquid crystal panel and the analyzer (that is, close to the exit side of the liquid crystal panel), and the optical compensator compensates for the phase shifts due to the pretilt angles (i.e., phase shifts between extraordinary light and ordinary light in the planes parallel and perpendicular to the panel surface) by the birefringence of the optical compensator when light passes through the liquid crystal molecules after entering obliquely into the liquid crystal panel.
Light exiting from the liquid crystal panel after entering obliquely into the liquid crystal panel through pixels to display black decreases in transmittance when passing through the analyzer, because the optical compensator compensates for the phase shifts due to the pretilt angles and thus fewer linearly polarized light components pass through the analyzer. Therefore, a smaller quantity of light is projected onto a screen from the liquid crystal panel through the pixels to display black (that is, black is prevented from standing out), so that deterioration in contrast due to properties of dependence on viewing angles is prevented.
Even when cell gap lengths vary according to parts of the individual liquid crystal panels (that is, the degrees of phase shifts due to the pretilt angles differ among the parts), or even when the cell gap lengths differ among a plurality of liquid crystal panels (that is, the degrees of phase shifts due to the pretilt angles differ among the liquid crystal panels), the optical compensator compensates for the phase shifts due to the pretilt angles, so that deterioration in uniformity due to the properties of dependence on viewing angles is prevented.
If the optical compensator is located between the polarizer and the liquid crystal panel (that is, close to the entry side of the liquid crystal panel), light entering into the liquid crystal panel via the optical compensator is focused on the liquid crystal molecules by the microlenses and enters into the liquid crystal molecules, so that an incident angle of the light to the optical compensator differs from an actual incident angle of the light to the liquid crystal molecules. The degree of phase shifts due to the pretilt angle is determined by the actual incident angle of the light to the liquid crystal molecules. As a result, when the optical compensator is located close to the entry side, it becomes difficult to optimally compensate for the phase shifts due to the pretilt angle according to the actual incident angle of the light to the liquid crystal molecules.
On the other hand, when the optical compensator is located close to the exit side of the liquid crystal panel as in the case of the above-described liquid crystal projector apparatus, an actual incident angle of light to the liquid crystal molecules is equal to an exit angle of the light from the liquid crystal panel, so that an incident angle of the light to the optical compensator becomes equal to the actual incident angle of the light to the liquid crystal molecules. Therefore, it becomes easy to optimally compensate for the phase shifts due to the pretilt angle according to the actual incident angle of the light to the liquid crystal molecules.
Preferably, as an example, a phase difference film (generally called xe2x80x9ca uniaxially oriented phase difference filmxe2x80x9d) having birefringence only in a plane parallel to a film surface is located at an angle to a panel surface of the liquid crystal panel so as to function as the optical compensator.
To allow linearly polarized light having a direction of vibration perpendicular to the polarizer and the analyzer to pass through the polarizer and the analyzer (that is, in normally white mode), it is preferable as an example that either a phase delay axis or a phase advance axis of the uniaxially oriented phase difference film be perpendicular to a polarization axis of the polarizer (or the analyzer) and the uniaxially oriented phase difference film be inclined about an axis parallel to the polarization axis of the polarizer (or the analyzer).
This permits compensating for the phase shifts due to the pretilt angle on the entry side (or the exit side) independently of the phase shifts due to the pretilt angle on the exit side (or the entry side).
Furthermore, both the uniaxially oriented phase difference film whose phase delay axis or phase advance axis is perpendicular to the polarization axis of the polarizer and the uniaxially oriented phase difference film whose phase delay axis or phase advance axis is perpendicular to the polarization axis of the analyzer may be located. This allows compensating for both the phase shifts due to the pretilt angle on the entry side and the phase shifts due to the pretilt angle on the exit side independently of each other and therefore allows still more greatly enhancing the effect of improving the contrast and the uniformity.
Preferably, as another example, a phase difference film (generally called xe2x80x9ca special biaxially oriented phase difference filmxe2x80x9d or xe2x80x9ca viewing angle increasing filmxe2x80x9d) having birefringence in planes parallel and perpendicular to a film surface is located parallel to the panel surface of the liquid crystal panel so as to function as the optical compensator. This allows minimizing the increase in a distance between the liquid crystal panel and the analyzer and therefore allows contributing to the downsized optical system of the liquid crystal projector apparatus.
A method of improving contrast of the invention of a liquid crystal projector apparatus including: a liquid crystal panel having microlenses for focusing incoming light on effective display area portions of pixels, the liquid crystal panel for changing a locus of a resultant electric field vector of light passing through liquid crystal molecules according to a voltage applied to the liquid crystal molecules; a polarizer for allowing linearly polarized light, which is contained in light emitted from a light source and has one direction of vibration, to enter into the liquid crystal panel; and an analyzer for allowing linearly polarized light, which is contained in light exiting from the liquid crystal panel and has one direction of vibration, to enter into a projection optical system includes: a first step of locating a first phase difference film between the liquid crystal panel and the analyzer, the first phase difference film having birefringence only in a plane parallel to a film surface and inclined at an angle to a panel surface of the liquid crystal panel; a second step of checking transmittance of light exiting from the liquid crystal panel through pixels to display black when the exiting light passes through the analyzer, while varying an angle of inclination of the first phase difference film, and then determining the angle of inclination according to the magnitude of the transmittance; a third step of calculating the magnitude of retardation of the first phase difference film in planes parallel and perpendicular to the panel surface, when the first phase difference film has the angle of inclination determined by the second step; and a fourth step of locating a second phase difference film instead of the first phase difference film between the liquid crystal panel and the analyzer in parallel with the panel surface, the second phase difference film having birefringence in planes parallel and perpendicular to a film surface and having the magnitude of retardation in the planes parallel and perpendicular to the film surface which is approximately equal to the magnitude of retardation in the planes parallel and perpendicular to the panel surface calculated by the third step.
In the method of improving contrast, the first phase difference film (the uniaxially oriented phase difference film) having the birefringence only in the plane parallel to the film surface is located at an angle to the panel surface of the liquid crystal panel between the liquid crystal panel and the analyzer, the transmittance of light exiting from the liquid crystal panel through the pixels to display black is checked at varying angles of inclination of the uniaxially oriented phase difference film when the exiting light passes through the analyzer, and then the angle of inclination of the uniaxially oriented phase difference film is determined according to the magnitude of the transmittance.
This allows determining the angle of inclination of the uniaxially oriented phase difference film so as to reduce the transmittance of light exiting through the pixels to display black when the exiting light passes through the analyzer (that is, so as to compensate for the phase shifts due to the pretilt angle).
Moreover, the uniaxially oriented phase difference film is located between the polarizer and the liquid crystal panel (that is, close to the exit side of the liquid crystal panel), and thus an incident angle of light to the uniaxially oriented phase difference film becomes equal to an actual incident angle of the light to the liquid crystal molecules. Therefore, it becomes easy to determine the angle of inclination so as to optimally compensate for the phase shifts due to the pretilt angle according to the actual incident angle of the light to the liquid crystal molecules.
In the method of improving contrast, subsequently, the magnitude of retardation of the uniaxially oriented phase difference film in the planes parallel and perpendicular to the panel surface is calculated when the uniaxially oriented phase difference film has the determined angle of inclination. Then, instead of the uniaxially oriented phase difference film, the second phase difference film (the viewing angle increasing film), which has the birefringence in the planes parallel and perpendicular to the film surface and has the magnitude of retardation in the planes parallel and perpendicular to the film surface that is approximately equal to the calculated magnitude of retardation in the planes parallel and perpendicular to the panel surface, is located parallel to the panel surface between the liquid crystal panel and the analyzer.
When an image is displayed by the liquid crystal projector apparatus having the above-described viewing angle increasing film, a smaller quantity of light is projected onto the screen from the liquid crystal panel through the pixels to display black, and therefore the deterioration in contrast due to the properties of dependence on viewing angles is prevented, so that the contrast is improved.
Even when the cell gap lengths vary according to parts of the individual liquid crystal panels, or even when the cell gap lengths differ among a plurality of liquid crystal panels, the phase shifts due to the pretilt angles are compensated for as described above, and thus the deterioration in uniformity due to the properties of dependence on viewing angles is prevented, so that the uniformity is improved.
Moreover, the viewing angle increasing film is located parallel to the panel surface, and this allows minimizing the increase in the distance between the liquid crystal panel and the analyzer and therefore allows contributing to the downsized optical system of the liquid crystal projector apparatus.
Furthermore, the above-described method can prevent the deterioration in contrast and uniformity due to the properties of dependence on viewing angles, even if the method is applied to a transmission type liquid crystal projector apparatus having liquid crystal panels having no microlens for increasing a numerical aperture. Therefore, the method of improving contrast and uniformity can be also put to common use for both a transmission type liquid crystal projector apparatus having liquid crystal panels each having microlenses and a transmission type liquid crystal projector apparatus having liquid crystal panels having no microlens.
Also in the method of improving contrast, to allow linearly polarized light having a direction of vibration perpendicular to the polarizer and the analyzer to pass through the polarizer and the analyzer (that is, in normally white mode), it is preferable as an example that, in the first step, either a phase delay axis or a phase advance axis of the uniaxially oriented phase difference film be made perpendicular to a polarization axis of the polarizer (or the analyzer) and the uniaxially oriented phase difference film be inclined about an axis parallel to the polarization axis of the polarizer (or the analyzer).
This permits compensating for the phase shifts due to the pretilt angle on the entry side (or the exit side) independently of the phase shifts due to the pretilt angle on the exit side (or the entry side).
Furthermore, the second, third and fourth steps may be performed when either the phase delay axis or the phase advance axis of the uniaxially oriented phase difference film is perpendicular to the polarization axis of the polarizer and when either the phase delay axis or the phase advance axis of the uniaxially oriented phase difference film is perpendicular to the polarization axis of the analyzer. This allows compensating for both the phase shifts due to the pretilt angle on the entry side and the phase shifts due to the pretilt angle on the exit side independently of each other and therefore allows still more greatly enhancing the effect of improving the contrast and the uniformity.
Preferably, the method of improving contrast further includes a fifth step of making fine adjustment of a rotational angle position of the viewing angle increasing film in the plane parallel to the film surface, after the fourth step of locating the viewing angle increasing film.
Fine adjustment can be performed for the magnitude of birefringence in the plane perpendicular to the panel surface by making fine adjustment of the rotational angle position of the viewing angle increasing film as described above. Therefore, the contrast and the uniformity can be improved by making fine adjustment of the magnitude of birefringence, even after the viewing angle increasing film is located.
A projection type liquid crystal display apparatus of the invention comprises: a light source for emitting light required for image display; a transmission type liquid crystal display device having a liquid crystal layer having an alignment of a plurality of twisted liquid crystal molecules, the liquid crystal display device for selectively applying a voltage to the liquid crystal layer in response to an image signal, thereby realigning the liquid crystal molecules and thus modulating light passing through the liquid crystal layer; a first optical compensator located on a light exit side with respect to the liquid crystal display device and containing a substance having birefringence equivalent to birefringence of a negative crystal, the first optical compensator for compensating for an optical phase difference caused by liquid crystal molecules in a light-entry-side region of the liquid crystal layer; and a projection lens for projecting the light modulated by the liquid crystal display device.
Desirably, the projection type liquid crystal display apparatus of the invention further comprises a second optical compensator located on the light exit side with respect to the liquid crystal display device, the second optical compensator for compensating for an optical phase difference caused by liquid crystal molecules in the light-exit-side region of the liquid crystal layer.
Desirably, the projection type liquid crystal display apparatus of the invention further comprises a third optical compensator located on the light exit side with respect to the liquid crystal display device, the third optical compensator for compensating for an optical phase difference caused by liquid crystal molecules present in a region of the liquid crystal layer excluding the light-entry-side region and the light-exit-side region. Desirably, the third optical compensator is made of, for example, a substance having birefringence equivalent to birefringence of a negative uniaxial crystal. For example, in the case where each of the liquid crystal molecules in the liquid crystal layer has birefringence equivalent to birefringence of a positive uniaxial crystal and where, in a state in which a voltage is applied to the liquid crystal layer, the liquid crystal molecules in the liquid crystal layer are realigned so that the major axes of the molecules change in position from a position parallel or about parallel to a plane of incidence of light to a position perpendicular or about perpendicular to the plane of incidence of light as they are situated farther from the light-entry-side region of the liquid crystal layer and closer to the center of the liquid crystal layer, the third optical compensator functions to compensate for an optical phase difference caused by the liquid crystal molecules aligned with the major axes thereof perpendicular to the plane of incidence of light. Desirably, molecules of the substance constituting the third optical compensator and having the birefringence are aligned so that the optic axes of the molecules are parallel to the major axes of the liquid crystal molecules to be compensated for, in a state in which a voltage is applied to the liquid crystal layer.
In the projection type liquid crystal display apparatus of the invention, the first optical compensator located on the light exit side with respect to the liquid crystal display device compensates for the optical phase difference caused by the liquid crystal molecules in the light-entry-side region of the liquid crystal layer.
In the projection type liquid crystal display apparatus of the invention, for example, in the case where each of the liquid crystal molecules in the liquid crystal layer has the birefringence equivalent to the birefringence of the positive uniaxial crystal and where, in a state in which a voltage is applied to the liquid crystal layer, the liquid crystal molecules in the liquid crystal layer are aligned so that the major axes of the molecules are perpendicular to the plane of incidence of light as they are situated farther from the light-entry-side region of the liquid crystal layer and closer to the center of the liquid crystal layer, the third optical compensator made of, for example, a substance having birefringence equivalent to birefringence of a negative uniaxial crystal compensates for the optical phase difference caused by the liquid crystal molecules aligned with the major axes thereof vertical.